Bas C. van Fraassen

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Identity over time: objective, subjective

B. van Fraassen and I. Peschard , Go to article in Philosophical Quarterly 2008.
In philosophy of science, identity over time emerges as a central concern in two guises: as an ontological category in the interpretation of physical theories, and as a problem in epistemology with respect to the conditions of possibility of knowledge. In Reichenbach's and subsequent writers on the problem of indistinguishable particles in quantum physics we see the return of a contrast between Leibniz and Aquinas on the subject of individuation. The possibility that the principle of the identity of indiscernables can be rejected has certain logical difficulties, which inexorably lead us from ontology into epistemology.
          For the epistemological problem we must attend to the differences that emerged between the (neo-)Kantian and logical empiricist traditions, also most saliently displayed in Reichenbach's writings. After an examination of the contrast between Kant's and Leibniz' conceptions of empirical knowledge, specifically with respect to the irreducibility of spatio-temporal determinations, we explore an application of a neo-Kantian view to that same problem of indistinguishable particles in physics.

Laws and Symmetry

Synopsis (book):

Laws and Symmetry has three main objectives. The first is to show the failure of philosophical accounts of laws of nature. The second is to undercut the epistemological principles at work in arguments for the reality of laws of nature. The third objective, nearest to my heart, is to be constructive as well, and to contribute to an epistemology and a philosophy of science antithetical to such metaphysical notions as laws of nature. Part One, in which the first objective is pursued, was the main subject of discussion in the symposium to follow. In this Synopsis, therefore, I shall concentrate on that.

In my view, as presented in Chapter 1, the concept of a law of nature is an anachronism, its proper life belonging to the 17th and 18th Centuries. Laws of nature played an important role in the philosophical-scientific thinking of Descartes and Newton, and functioned for them as a central clue to the structure of science. At the same time, two developments threatened the status of law. One was the empiricist critique of necessity and causality, notions closely allied to that of law. The other was that science was rapidly gaining autonomy not only from theology but from all of philosophy, and was exploiting concepts and methods foreign to metaphysics. Pre-eminent here is the birth of the symmetry argument. (Discussion of this subject is begun in Chapter 1 and continued in Chapters 10, 11 and 12.) Modern physics argues from symmetry and continuity -- not from universality or necessity, natural kinds or essences, contingency or accident. The concept of a law of nature is a vestigial concept in contemporary science.

Chapter 2 collects the cluster of criteria for what laws must be and do, which are honored in the literature to some degree or other. We can divide the criteria to be met by any philosophical account of laws roughly into major requirements and secondary ones. The major criteria concern what I call the problems of inference and identification. The accounts must show that there is a valid inference from what laws there are to what regularities there are in the world. The account must also identify the relevant aspects of the world that constitute or give rise to its laws, if any. Typically these two tasks lead to a dilemma. If laws of nature are identified in terms of some sort of necessity in nature which is simply postulated as fact, then there is no logical reason to think that the inference from lawlike necessity to actuality is valid. (Calling the postulated factor "necessity" or "necessitation" does not help.) If on the other hand the semantic account of law statements is so constructed that the inference in question is logically valid, then typically the truth-conditions of law statements involve something unidentifiable. Chapters 3, 4, and 5 argue that leading contemporary attempts (by David Lewis, David Armstrong, and a host of others) fail to slip between the horns of this dilemma. Nor do they meet secondary criteria, such as showing that what they make out to be laws of nature are the targets reached, or even aimed for, in scientific inquiry.

Both Quine and Rorty have, in their different ways, proclaimed the death of epistemology. I think they are right about mainstream traditional epistemology. There Induction has given way to Inference to the Best Explanation (IBE) in the epistemology hospitable to realism, or to metaphysics in general. In my view, developed in Part Two, neither Induction nor IBE qualifies as a rational strategy for change of opinion. To that extent at least I endorse some of Quine's and Rorty's conclusions. But it also seems to me that the underground river of probabilism, slowly growing in force over three centuries, has burst forth above ground in the twentieth century and brought new hope for epistemology. In Part Two I argue that with the end of foundationalism, probabilism provides the framework for a new epistemology, which is also adequate for philosophy of science.

The remainder of the book (Chapters 8-13) is devoted to contributions to the semantic approach in philosophy of science, to support my call to leave metaphysics behind. The semantic approach does not require an anti-realist or anti-metaphysical stance. In fact it is also followed by philosophers with very different philosophical positions from my own. But that is just the point: this collaboration in philosophy of science is possible because the approach is in itself neutral, and does not presuppose metaphysical views. I will leave the details aside, since the present symposium concentrates on Part One, which was meant to be the destructive prelude to this constructive effort in philosophy of science.

For current availability, Laws and Symmetry

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The Manifest Image and the Scientific Image

pp. 29-52 in D. Aerts (ed.). Einstein Meets Magritte: The White Book -- An Interdisciplinary Reflection. Dordrecht: Kluwer, 1999.

To read this on the web, go to "The Manifest Image and the Scientific Image"


There are striking differences between the scientific theoretical description of the world and the way it seems to us. The consequent task of relating science to 'the world we live in' has been a problem throughout the history of science. But have we made this an impossibility by how we formulate the problem? Some say that besides the successive world-pictures of science there is the world-picture that preceded all these and continues to exist by their side, elucidated by more humanistic philosophers. Wilfrid Sellars codified this conviction in his dichotomy of scientific image and manifest image. Others say that all our world-pictures are transient, evolve, conflict with and replace each other, undergo violent revolutions as well as periods of normal development, and may be incommensurable, allowing of no meaningful dialogue. All such formulations may themselves be tendentious metaphysics, full of false contrasts. Insistence on a radical separation between science and what we have apart from science, on the impossibility of accommodating science without surrender, may be a way of either idolizing or demonizing science rather than understanding it.

Modal Interpretation of Repeated Measurement:

Rejoinder to Leeds and Healey

Philosophy of Science 64 (1997): 669-676.

A recent article (Leeds and Healey, 1996) argues that the modal interpretation (Copenhagen variant) of quantum mechanics does not do justice to immediately repeated non- disturbing measurements. This objection has been raised before, but the article presents it in a new, detailed, precise form. I show that the objection is mistaken.

Structure and Perspective: Philosophical Perplexity and Paradox

pp. 511-530 in M. L. Dalla Chiara et al. (eds.) Logic and Scientific Methods. Dordrecht: Kluwer, 1997.

to read this paper on the web, and skip the abstract, go to "Structure and Perspective: Philosophical Perplexity and Paradox"

This paper has two abstracts


In reaction to revolutionary developments in modern science, both philosophers and scientists have suggested that science describes only the structure, as opposed to content, of the world. The described structure is structure invariant under changes of perspective (frames of reference, observers, alternative measurement set-ups). Extrapolating the view too far, the disappearance of content and of individual perspective leaves us with structure itself as surrogate content for a logically incoherent view from nowhere. Both empiricism and scientific realism face a quandary, with attempts to find a 'foundation' for science outside what is described in physical theory (whether qualities of experience or a postulated 'ready-made' world) notably lacking in success. I this paper I shall re-examine the prospects for a view of science which is empiricist but not foundationalist.


Structuralism (one variety of): the view that science describes only the structure (and not the content) of its domain. A view entangled from the beginning with the view that science is a representation of nature.

There were and are good reasons to be attracted to structuralism. But it needs to be explained, for as stated it rests on an obscure and possibly untenable distinction between structure and content.

Problem: attempts to make it precise have tended to reduce it to absurdity. Example: the Ramsey sentence view is a moderate form of structuralism. Lewis' postulate of natural classes can then be read as an attempt to rescue it from the reductio. Elgin's criticisms and Laurie Paul's 'symmetry' objection may be read as saying that this sort of rescue cannot work.

My Problem: my view of science belongs to the "semantic approach" which is pretty clearly a form of structuralism (though certainly as moderate as the Ramsey sentence version, in its deference to our understanding of "old" terms). I argue that it does not reduce to absurdity because the structuralism pertains to the raw materials for representation (the models which are used to represent) and not to the representing activity.

========= PS: the first section of "From Vicious Circle ..." is a further reflection on this topic.

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